1. Field of the Invention
The present invention relates to an ink cartridge for use in an ink jet recording apparatus for recording images, characters, and the like on a recording sheet by ejecting ink droplets from a nozzle, and to a recording apparatus including the ink cartridge.
2. Related Background Art
At present, there are provided many ink jet recording apparatuses (ink jet printers) for recording images, characters, and the like by ejecting ink droplets on a medium on which recording is effected, such as a recording sheet. In the ink jet printer, ink is supplied to a recording head through an ink supply pipe, and ink droplets are ejected from a nozzle of the recording head onto a recording sheet, thereby performing recording.
Further, in an ink cartridge generally used for an ink jet printer, an ink bag in which ink is sealed in advance is accommodated in a casing. The ink bag has flexibility, so according to an ink residual amount, a thickness thereof changes. By measuring the thickness of the ink bag, the ink residual amount is estimated. This is because the ink residual amount cannot be directly determined.
As a method for measuring the thickness of the ink bag, there are provided various methods. There is generally known a method, in which a plate is attached onto an upper surface of the ink bag, and a change in thickness of the ink bag is detected as a vertical displacement of the plate. According to the method, by detecting the displacement of the plate, the ink residual amount can be determined. Thus, by detecting a state where the plate arrives at a position corresponding to the ink residual amount of “zero”, it is possible to detect a state where the ink is used up.
However, for the recent ink bags, in order to ensure gas barrier property, an aluminum laminate film or the like is used as a material, and ink bags having higher rigidity of the ink back themselves come into use. Therefore, it is becoming difficult for the ink bags to smoothly deform according to the ink residual amount. Thus, it is difficult to detect the ink residual amount with a high degree of precision. In particular, the less the ink residual amount, the more conspicuous the deterioration in detection accuracy.
In this connection, there is known an ink cartridge capable of detecting the ink residual amount without being affected by the rigidity of the ink bag, for example, Japanese Patent No. 3141894.
In the ink cartridge, the ink bag is mounted so that the ink bag is not laid horizontally but faces sideways, that is, the plate fixed to the upper surface of the ink bag faces a vertical direction. Further, the plate is provided with a detection protrusion formed thereon for causing an external detection device to operate. The detection protrusion is formed so as to be positioned on a lower side of the ink bag when the ink cartridge is mounted. When the ink residual amount decreases, the detection protrusion protrudes to the outside from a window formed in the casing. Further, the detection protrusion which protrudes reaches an ink end detector (detection device) provided in an outside of the casing. When reached by the detection protrusion, the ink end detector detects a state where the ink is used up.
In particular, the ink bag is mounted so as to face sideways, so when consumption of the ink in the ink bag is started, the residual ink starts to gather in a lower portion of the ink bag due to the gravity. Note that in an initial state, the plate is inclined obliquely. When the ink gathering in the lower portion of the ink bag further flows out due to further ink consumption, the lower portion side starts to be crushed, so the plate moves so as to rotate about an upper portion of the ink bag as a center. As a result, the detection protrusion formed on the lower portion side of the ink bag moves toward the window of the casing to protrude to the outside of the casing. When the detection protrusion reaches the ink end detector, the detection of the ink residual amount is performed.
As described above, by moving the ink remaining in the ink bag to the lower portion side of the ink bag and rotating the plate, it is possible to displace the plate accurately according to the ink residual amount. Accordingly, even when the slightly rigid ink bag is used, it is possible to detect the ink residual amount without being affected by the rigidity. In particular, even when the ink residual amount is small, it is possible to detect the ink residual amount with a high degree precision.
However, there remains the following problems with the conventional ink cartridge.
That is, the conventional ink cartridge has such a structure that the ink residual amount is detected in response to arrival of the detection protrusion formed on the plate at the detector, so it is required to fix the plate accurately in a predetermined position on the ink bag. If a fixing position deviates from the predetermined position, there are possibilities that the detection protrusion does not protrudes from the window to the outside and that the detection protrusion reaches the ink end detector in advance while the ink bag is being deformed, thereby causing false detection.
In particular, the plate is adhered to be fixed to the ink bag by a double-sided adhesive tape or the like, so it is required to attach the plate while performing positioning carefully and accurately. Therefore, the attachment involves a great amount of time and effort. Further, even if the attachment operation is performed with care, the attachment accuracy involves no allowance, so there is a risk of the false detection being caused.
Further, the detection protrusion is formed on the plate fixed to the ink bag, so the detection protrusion moves in three dimensions in accordance with movement of the ink bag. Further, the ink bag does not move regularly every time, and is expected to move differently every time according to an installation state, frequency of use, or the like. Thus, a movement is not ensured in which the detection protrusion is allowed to protrude every time from the window according to the ink residual amount to be allowed to reach the ink end detector. In this point also, there is the possibility of causing the false detection.